The commodity electronics of today require more and more function be packed into an ever decreasing space. This trend has given us cellular telephones that can record movies and send them across the internet to be downloaded by a computer, moments after the recording. We also have personal audio/video players that can store thousands of songs or hundreds of music videos. With the shrinking size of devices, the increasing function and commodity pricing, immense pressure is put on the packaging technology to make it all work in less and less space.
There are a number of conventional processes for packaging integrated circuits. In many situations it is desirable to incorporate multiple integrated circuit dice into the same package in what is commonly referred to as a multi-chip package. Some multi-chip packages are arranged to stack two or more dice on top of each other. These stacked die packages have several potentially beneficial aspects including the possibility of a reduced die or package footprint and certain performance aspects (e.g., by reducing the path length of electrical connections between integrated circuits and thus potentially increasing speed and reducing inductance of inter-chip communications).
In order to facilitate the shrinking package size and increasing performance, many of today's designs utilize ultra-thin wafers that are difficult to handle due to their fragility. In a stacked die environment, with ultra-thin die, yield issues have a serious impact on the cost and performance of the finished packages. Semiconductor wafers such as thin monocrystalline silicon wafers are commonly used in semiconductor device fabrication. These wafers can have any desired diameter, for example, 1″ to 12″ and have varying thicknesses, typically about 300 to 600 microns. The entire wafer is photolithographically processed, receiving on its top surface a large number of spaced sets of diffusions, oxidations, etches, washes, metal layers and the like to form a large number of identical devices such as transistors, diodes, and other such devices. After processing, the wafers are frequently thinned by grinding from the wafer back surface to a thickness desired to satisfy a desired characteristic of the device. The individual devices are then separated by cutting through the wafer.
Many recent semiconductor devices have a need for ultra-thin semiconductor die. For example, Insulated Gate Bipolar Transistors of the “punch-through” type and with a “transparent” collector region and rated at 600 volts or more can be made in wafers about 100 microns thick. Other voltage ratings require even thinner wafers, some as thin as 70 microns. These ultra-thin die require special handling to prevent damage in the package assembly processes. Many of the devices are damaged during the device separation process or fail due to stresses applied to them during the interconnect or die stacking processes. The number of devices used in the commodity electronics devices today demand that 30 to 40% additional devices be manufactured to meet the demand and bridge the yield problems with the ultra-thin semiconductor die. To date the over-manufacture of ultra-thin semiconductor die is accepted as a compromise solution to meet the demand.
Thus, a need still remains for an integrated circuit packaging system with ultra-thin die that can address the fragility of the die and group multiple devices in a single package. In view of the constant advance of technology, with ultra-thin devices and multiple device packages, it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, these problems must be addressed quickly and effectively. Additionally, the need to save costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.